1. Field
This disclosure relates generally to semiconductor devices, and more specifically, to semiconductor devices that utilize a stressor.
2. Related Art
One of the techniques for improving performance of MOS transistors is to provide stress to the channels. Providing tensile stress to the channels of N channel transistors increases electron mobility to enhance performance. Providing compressive stress to the channels of P channel transistors increases hole mobility to enhance performance. A variety of techniques have been developed to achieve these results. One is to provide a recess in the source/drain regions and then regrow the source/drain region with a semiconductor stressor material that provides stress to the channel. Another technique is to deposit a film, after gate formation, that has stress that is transferred to the channel. Under proper circumstances the stress of the deposited film can be transferred to the channel and then retained by the channel even after the deposited film has been removed. These approaches and combinations of these approaches tend to cause other problems.
Thus there is a need to be able to use multiple stress inducing techniques while reducing the problems associated with combining the multiple techniques but not at the expense of losing the intended stress benefit.